An observer moves towards a stationary source of sound with a velocity of one fifth of the velocity of sound. The percentage increase in the apparent frequency is

Step-by-step solution

Doppler effect for observer moving toward stationary source : apparent frequency f' = f ( v + v_o v ) , where f is source frequency, v is sound velocity, and v_o is observer velocity. Given observer velocity v_o = v 5 , substitute to obtain: f' = f ( v + v 5 v ) = f ( 6v 5 v ) = 6 5 f = 1.2f The percentage increase is: f' - f f 100 % = 1.2f - f f 100 % = 0.2 100 % = 20 % The apparent frequency increases by 20 % .